1. Field of the Invention
The present invention relates to a color filter for use in a liquid crystal display (LCD). In particular, the present invention relates to the formation of a color filter using a novel black matrix design thereof that can improve the light filtering performance of the pixel.
2. Descriptions of the Related Art
LCDs have replaced conventional displays and have become mainstream products due to their low power consumption, light weight, low radiation and portability. In general, a LCD comprises main components including the backlight module, the liquid crystal panel, and the color filter. Among these main components, the color filter is a key component to filter the backlight source into red, green, and blue through every arranged pixel.
In a conventional manufacturing of color filters, a black matrix comprising a plurality of frame structures in correspondence to a plurality of pixel areas is first formed on a substrate to accommodate the color filter layers that prevent light leakage and undesired color mixing between adjacent pixels. The black matrix generally consisting of photosensitive materials is photolithographically formed and cured by baking or ultraviolet light exposure to strengthen these bank-like frames.
FIG. 1 is a schematic side view partially illustrating the color filter 10 on a single pixel, and showing the conventional ink-jet printing (IJP) process. Specifically, after a plurality of frames 13 are formed on the substrate 11, ink 21 can be jetted into each frame 13 to form a color filter layer 15 with a specific color. After that, a baking process is followed to take on its final shape. When the light passes through the color filter layer 10, the specific color will be shown in each pixel. The combination of all pixels can be well arranged to provide chromatic variety for the use of LCD.
However, there exist some difficulties in the ink-jet color filter manufacturing process. For example, when ink 21 is jetted to the substrate 11 through a nozzle 20 with a high speed, the ink 21 probably flows over the frame 13, leading to a color mixing problem.
Furthermore, due to the surface tension of jetted ink in a frame 13, the formed color filter layer 15 becomes uneven that the surface contour is higher at the pixel center and even higher than the frame 13. This color filter is thus no longer flat after the baking process that will influence the step coverage of the subsequent deposition or coating processes. As shown by the dashed lines in FIG. 2, specifically, the higher surface tension at the center of a pixel 15 causes not only the uneven issue, but also the insufficient filling in four corners of the pixel resulting to light leakage. The display quality is therefore degraded, especially at the corners along the minor sides in the rectangular frame structure.
Therefore, a novel design of a color filter and a black matrix thereof is proposed to improve above-mentioned issues for the ink-jet color filter applications.